He has become the assistant to guest conductors – a job rarely given to someone so young. The role involves being on standby to conduct the orchestra if guests are forced to cancel their engagements.

"Serving on the conducting staff of a major orchestra is a key professional development opportunity for young conductors, although most are not given the opportunity at such a young age," a statement from the Seattle Symphony said.

Announcing the appointment, Leslie Jackson Chihuly, the chairman of the symphony's board, said: "We are thrilled to have such a promising young conductor as Alex Prior joining our conducting team.

"His work will be an asset to us, and we look forward to nurturing his artistic development."

Prior, who was born in October 1992 and made his conducting debut with the National Symphony Orchestra in March 2007, will combine his role with studies at the St Petersburg Conservatory, in Russia.

The musician – the great-great-grandson of the founder of method acting, Constantin Stanislavski – is best known for presenting a three-part Channel 4 series, the World's Greatest Musical Prodigies, last year. He was the runner-up in the 2009 Leeds conductors' competition.

However, his style is not to everyone's taste. The Guardian's classical music critic, Tom Service, said Prior came across with "priggish bumptiousness born of unshakeable self-confidence" on his TV series.

Service also described his compositions, which include Mowgli, a ballet based on the Jungle Book, as "quaintly nostalgic".